Luminair



Aug. 15, 1933. "r; w. RoL'PH. 1,922,331

' LUMINAIR Filed Sept. 23, 1952 4 Sheets-Sheet 2 INVENTOR. Thomas WRolp'z DLreczwn 5. rfroad BY kmmm.

ATTORNEY.

T. W. ROLF'H Aug. 15, 1933.

LUMINAIR Filed Sept. 23, 1932 4 Sheets-Sheet 3 INVENTOR. Thomas WRolph BY ATTORNEYI action- 9 mad.

Aug. 15, 1933. 1' w RQLPH 1,922,331

LUMINAIR Filed Sept. 25, 1932 4 Sheets-Sheet 4 Zenith Jl'i'eel jla'e Wriz'cal angle House Jide.

W 60. Nadir lateral angle l ir' g" INVENTOR of ma 7 Thomas WBzIlP BY gaug A TTORNEK Fig. 9

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Poteuted Au 15, 1933 (UNITED STATES PATENT OFFICE Application September 23, 1932 Serial No. 684,452

18 Ca. (Qt. bill-"166) The present invention relates to lumixmirs, and is more particularly directed toward lumiuairs employing refractors for light control. It relates to on improvement in rciroctors, and is of parvticulor value for highway lighting but may also be used for other classes of lighting where a long narrow area. is to be illuminated.

In the lighting of outdoor areas, such as streets and highways, it is customary to space the luminuirs at considerable distances apart. Such.

spacing provides the greatest economy in cost of installation and operation, consistent with ob-' mining good lighting results. A spacing which is generally considered satisfactory is 8 times the mounting height but other ratios of spacing. to height varying widely from this are frequently used. Small spacing ratios in the neighborhood of l 'to 4 times the mounting height src rarely used and are uneconomical. When a long narrow strip of roadway such as on inter-urban highway is illuminated, the light should be confined within a. narrow lateral angle.

If such a. strip is lighted by lmits spaced at the customary distances apart, an attempt to spread the light with reasonable uniformity over the area. will result in very high candle-power toward the point midway between units. This candle power will be much higher than is the case when light is distributed with reasonable uniformity ovor wider roadways such as city streets. This will bc clear from an example.

If u lair is so designed as to illuminate with reasonable approach to uniformity an area '70 ft. wide and 200 ft. long, the useful flux is distributed over 14,000 square feet. If the luminair is placed at the center of the area,-the candlepower will be highest in the direction toward the edge approximately 100 ft. away. .City streets are customarily '10 to 80 ft. wide but interurban highways are usually much narrower, the two lane highway'being '18 ft. to 20 ft. wide ordinarily. If a luminalr is designed to illuminate this narrower roadway with the some light distribution as on the wider roadway, the light would be confined to on area approximately 208200 ft. and would be distributed over 4,000 square. feet v instead of 14,000 square feet. Therefore, the candlepower in all direction: toward this-area willbehizhcrmtheratloof 14ooo I ttoward the extreme edge of the area. the hizh in'tbeflnt case our! 55 wlllbeoomoextremolyhkhintholottorcaoe.

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Points onthestreet hallway between units are at high angles from the nadir of the loir and high candlepowor at such angles causes blurb. It has been found desirable, in facing such a. prob-- lem, to design the luminulr to provide a. certain 63 limited ca dlepower toward the extreme edge of the area. or in other words toward the eye of an. observer about hallway between lirs. By limiting the caudlcpowei' to a cortoiu mammoth value in such directions, glare toward the eyes of @5 a. motorist is kept sumcicntly low to be irmocuous.

Such limitation at tho angle of maximum coudlepowcr means that an excess twilight is left to be delivered at other angles. The rah-actor will, therefore, be designed to deliver this excess light m to the area, to be illuminated below the angle oi maximum and to distribute the light proporly over this area.

It will usually be found that when the illnation is non-uniform, the most desirable distriw bution provides the maximum illumination directly under the unit with gradually in m 511mg values to the minimum halfway between units. Such a. distribution of illumination provides conditions which reveal nearby objects by direct so illumination and distant objects by silhouette as dark outlines against a. lighter background. The light background in this case is the roadway which appears bright from a distance because of light reflected diffusely and specularly from the poveso ment.

This non-uniform distribution of light is not entirely satisfactory for direct illumination whereby objects are seen more completely than bysilhouette. However, in highway lighting the principal purposeof the lighting is to provide freedom from collision. Silhouette is quite satisfactory for this purpose. Other purposes of street lighting such as safety from attack and burglary, and convenience in recognizing passersby, etc., which require a. more uniform distribu- "tion of illumination are not of great importance in the lighting of inter-urban highways because such highways are primarily for the use of motorists rather then pedestrians. The motorist can stop underneath a. luminair illumination. It mtherefore, desirable for narrow highways, I

if he desires intense to limit the candlepowerof' the maximum beam of light thus avoiding excessive glue and to 106- use the surplus light to build up the illumination beneath the lummoir and at neorby points to o higher-value than the illumination half-way botween luminalra.

2 showing lateral distribution about a vertical axis, and-Fig. 3 verticaldistribution through the main beam and across the street or road;

Fig. 4 is a vertical sectional view taken in a plane across the road or street (or the line 4-4 of Fig. 5), the inner piece of the refractor being largely shown insection;

Fig. 5 is a top plan view of the inner glass part to show the disposition of the prisms;

Fig. 6 is an elevational view of the outer glass part, the prisms being indicated in dotted lines;

Fig. 7 is a top plan view of the outer retracting member, showing the distribution of the vertical prisms therein;

Fig. 8 is a horizontal sectional view taken on the line 8-8 oi Fig. 4 to illustrate the control of light by the double vertical retracting prisms; and

Fig. 9 is a projection of a hemisphere, similar to a Mercator's projector, with light source at the center and cated.

In Fig. 1, a typical highway is shown with the luminair mounted a short distance in from one edge '01 the highway. The various vertical and lateral angles 01' light intercepted by the highway are shown in this illustration. It willbeseen that in'the vertical plane, running directly across the street, the light should be spread from about 20 back of the unit to about 50 out from the unit across the street. The maximum candlepower along the street would ordinarily be delivered at the vertical angle, as indicated in full lines in Fig. 3. At this vertical angle, the lateral spread is from about 5 back 01' the unit out to about 20 out from the unit across the street. The distribution at right angles to the curb line is indicated by the dotted curve of Fig. 3. It is clear that at the angle of maximum candlepower, a relatively small lateral spread (in this case 25) is desirable for highway lighting. It has been pointed out above that if the light available for distribution on the highway is distributed to give uniform illumination, the maximum candlepower in this relatively small lateral zone will be extremely high and to avoid this, the maximum candle-power should be limited and the additional light distributed along the highway below this angle.

The refractor for effecting the desired distribution of light is shown in the form of a two piece refracting bowl open at the top. The inner bowl 10 (Fig. 4) is smooth inside and carries vertical and horizontal prisms on the outer surface. The outer bowl 11 may be rippled on the outside and carries vertical prisms on the inner surface. The inner bowl is made in a split mold having three 90 parts and two 45 parts, the dividing lines of the mold being indicated at M, N, O, 1?, Q, of Fig. 5. These mold lines form convenient limits for the horizontal prisms of different forms employed.

A large part of the half of the refractor which is toward the street (i. e. the part on the left of Figs. 4-9, inclusive) uses horizontal re- Iracting prisms on the outer surface of the inner glass part as shown at A, and vertical refracting important zones of light inditwo piece refractor provided with prisms for disprisms a on the imier surface of the outer glass part whereby light is concentrated at the desired vertical angle with the desired lateral spread, and light is also distributed below this vertical angle with a continually increasing spread as the vertical angle decreases. The retracting prisms A extend from M to'N and from.() to P for the entire height of the refractor and occupy the lower part of the refractor between N and O. The

house side of the outer reiractor is provided with vertical retracting prisms a which extended the entire height of the refractor. These prisms act on light received throughprisms A to direct it lengthwise oi. the road withthe desired vertical angle and lateral spread. This zone is designated as Ad in Fig. 9. Near the bottom of this portion of the reiractor, both the horizontal and vertical prisms become veryshallow or may be omitted since little light redirection is necessary.

On the right-hand portion or house side of the inner r eiractor a certain zone B extending from M to P carries reflecting prisms designed to return the light back through the light source 7 to be handled by the prisms below the light source in zone A on the opposite side. This is indicated by the ray 12 in Fig. 4. Zone C of the inner rei'ractor is made up of vertical, totally reflecting prisms. These vertical, totally reflecting prisms do not return the light back on its own path as the horizontal, totally reflecting prisms do. The

vertical prisms reflect the light in the same way that a mirror would reflect it with the angle of reflection equal to the angle oi. incidence. Since the top of these prisms is on a level with the light source and the prisms extend downward from this point, all light reflected from them is directed across the reflector below the light source. This light is handled by the retracting prisms on the opposite side of the refractor and distributed over the street area at angles below the angles at which the direct light is distributed. In this particular case a small section of these vertical reflecting prisms is preferable to the continuation of the band of horizontal reflecting prisms because the latter would tend toreflect light back to reflectinginstead oi retracting prisms on the opposite side of the refractor.

The house side of the inner refractor 10 has a series of vertical prisms D extending from M to Q and a similar series D extending from Q to P, of opposite sign, these prisms being placed below the totally reflecting prisms C. The street side oi the inner refractcr has, near the top, a series oi totally reflecting prisms E, similar to the prisms B, and acting on light as indicated by the ray 13. This reflected light, as well as certain direct light, is received. by the vertical prism bearing zones D-D'. The prisms D-D' are opposite vertical prisms a carried by the outer reiractor part 11. This prism arrangement makes it possible to obtain a much greater lateral deviation of light than can be obtained with vertical prisms on a single surface. It is possible to use this new feature of double vertical prisms giving great lateral deviation to the light, because the particular distribution of light required, as pointed out above, does not need vertical redirection of light which is emitted from the light-source below the angle of maximum, in this case 75. The problem is to get this light onto the highway at any angle below the angle of maximum. Double vertical refracting prisms will do this more eiiiciently than constructions which have been used zone D-Df can be handled makes possible the use of a second zone of reflecting prisms E on the upper part of the opposite side of the refractor.

these relative zones and the distribution of light required- This figure is a projection (similar to Mercators) of a hemisphere with the lightsource at the center and the various lateral and vertical angles designated. The vertical angles run from 0, the nadir, through 90, the horizontal, to 180, thezenith. The lateral angles run from 0, which is directly across the street from the luminair, through 90, which is parallel to a the direction of the street, to 180, which is directly back away from the street.

The light distribution required as illustrated in Fig. 1 is shown by the area F in this diagram. The area of' the refractor which carries the customary combination of horizontal and vertical refracting prisms is shown by area Aa. This corresponds to area A of Fig. 2. The reflecting prisms in area B of Figs. i and 5 are indicated as area B in this diagram. The double vertical refrecting prisms which form a new feature in refractor construction are used in area D. The horizontal reflecting prisms used in area E are made possible by the use of the double vertical prisms in area D.

Theoretically no redirection of light is neces-' sary in area F but actually prisms in sections Aa and D may extend over into area F in order to obtain the most effective distribution of light within the zone to be illuminated.

It should be understood that the angles shown in the diagrams and referredto herein are typical angles of a certain condition met with in illuminating highways. The invention may be used to obtan distributions varying considerably from this example. The zones using the different types of prismsindicated may be changed considerably in relative size and position. Threfore,

. the invention must not be considered as limited using prisms on both theinner surface and the outer surface, co-operating in the same general manner as when two pieces are used.

It is obvious that the invention may be embodied in many forms, and constructions, and I wish it to be understood that the particular form shown is but one of the many forms. modifications" and changes being possible, "I do not otherwise limit myself in any way with respect thereto.

What is claimed is:

1. A refractor, one section'of which concentrates light vertically and laterally, while another sectionconcentrates light laterally only, by means of two setsof parallel prisms carried on opposed surfaces ofthe refractor.

2. A refractor whose principal prismatic construction is divided horizontally into two parts,

Various the upper part carrying horizontal prisms on one surface and vertical prisms on an opposed surface and .the lower' part carrying vertical prisms on one surface and additional vertical prisms on an opposed surface.

3. A refractor, the upper part of which is adapted to produce concentration of light in both vertical and lateral directions, and the lower part. of which is adapted to produce concentration of light in lateral directions only, by means of two sets of vertical prisimsdisposed on opposed surfaces of the refractor.

4. A refractor whose principal prismatic construction is divided into two parts, the lower part carrying vertical prisms onone surface and addi tional vertical prisims on an opposed surface while the upper part is divided into sections some of which carry vertical prisms on one surface and horizontal prisms on an opposed surface while others ca'rry reflecting prisms adapted to return light to the lower section of the refractor for action by the prisms thereon.

5. A refractor adapted to concentrate light at a predetermined angle and carrying a double set of vertical prisms disposed on opposed surfaces of the refractor and adapted to control light emitted by thelight-source below this angle.

6. A refractor adapted to give a moderate concentration of light at a predetermined angle below the horizontal, the distribution of light being accomplished by controlling light from the source emitted above this angle by means of horizontal prisms'on one surface of the refractor and vertical prisms on an opposed surface of the refractor, while light from the source emitted below this v angle is controlled by vertical prisms on one surface of the refractor and additional vertical prisms on an opposed surface of the refractor.

'7. A luminair comprising a light-source and a light-controlling enclosure, one section of which carries means for reflecting light onto an opposite section, which transmits both direct and reflected light, and refracts it by means of a double set of parallel prisms disposed on opposed surfaces of the transmitting section.

8. A luminair comprising a light-source and a light-controlling enclosure, one section of which carries means for reflecting light back toward the light-source, while another section carries means for concentrating light in both vertical 125.

carries prisms for concentrating light'by refraction in lateral directions only.

10. A luminair comprising a light-source an a light-controlling enclosure, one section of which carries prisms-for reflecting light back toward the light-source, while another section carries prisms for concentrating light by refraction in both vertical and lateral directions and a third section carries prisms for concentrating light by refraction in lateral directions only.

11. A luminair comprising a light-source and a light-controlling enclosure, one section of which carries means for reflecting light back toward the light-source, while another section carries means for concentrating light in both crertical and lateral directions and a third section carries two sets parallel refracting prisms disposed on opposed surfacesv of the enclosure and adapted to concentrate light in lateral directions.

12. A luminair for road lighting and adapted to be mounted above the road, the luminair comprising a refractor having opposed vertical and horizontal prisms for producing beams of light concentrated in both vertical and lateral directions and directed obliquely downward toward the road surface, reflecting prisms on the upper house side of the refractor for reflecting light downwardly toward refracting prisms on the lower street side of the refractor which transmit this light as well as direct light downwardly to ward road surface adjacent the luminair to increase the inten'sity of illumination in this region.

13. A luminair for road lighting and adapted to be mounted above the road and to one side of the center thereof, the luminair comprising a refractor having opposed vertical and horizontal prisms for producing beams of light concentrated in both vertical and lateral directions and directed obliquely downward toward the road surface, reflecting prisms on the upper street side of the refractor for reflecting light downwardly toward opposed vertical prisms on the lower house side of the refractor which refract the reflected light as well as direct light laterally for building up the intensity of the main beams of light and preventing intense illumination of the region on the house side of the luminair.

14. A luminair for road lighting and adapted to be mounted above the road and to one side of the center thereof, the luminair comprising a refractor having opposed verticaland horizontal prisms for producing beams of light concentrated in both vertical and lateral directions and directed obliquely downward toward the road sur face, reflecting prisms on the upper house side of the refractor for reflecting light downwardly toward refracting prisms on the lower "street side of the refractor which transmit this light as well as direct light downwardly toward road surface adjacent the luminair to increase the intensity of illumination in this region, the refractor having reflecting prisms on the upper street side of the refractor for reflecting light downwardly toward opposed vertical prisms on the lower house side of the refractor which refract the reflected light as well as direct light laterally for building up the intensity of the main beams of light and preventing intense illumination of the region on the house side of the luminair.

15. A luminair for road lighting comprising a light source and a refractor, the refractor having in one quadrant on the "house side thereof totally reflecting horizontal prisms above the light source and opposed vertical prisms below the light source and of opposite sign with respect to the center of the quadrant, and horizontal refracting prisms extending throughout the other three quadrants except for a region of totally reflecting horizontal prisms on the street side above the light source and opposite the vertical prisms, and vertical prisms to receive the light from the horizontal refracting prisms and condense it into two narrow beams directed lengthwise of the road. 5

16. A luminair for road lighting comprising a light source and a refractor, the refractor having in one quadrant on the house side thereof totally reflecting horizontal prisms above the light source and opposed vertical prisms below the light source and of opposite sign with respect to the center of the quadrant, and horizontal refracting prisms extending throughout the other three quadrants except for a region of totally reflecting horizontal prisms on the street side above the light source and opposite the vertical prism, and vertical prisms to receive the light from the horizontal refracting prisms and condense it into two narrow beams directed lengthwise of the road, the vertical prisms on the street side of the refractor extending only through the upper part of the refractor so that refracted light may fall on the road surface at angles below the maximum without lateral deviation.

17; A luminair comprising a light source and a light controlling prismatic enclosure by which a portion of the light emitted from the source is concentrated both vertically and laterally at a predetermined angle and another portion of the light emitted by the .source is concentrated laterally at lower angles.

18. A luminair comprising a light source and a light controlling prismatic enclosure in which light emitted by the source above a predetermined angle is concentrated at that angle and light emitted by the source below the predetermined angle is concentrated laterally below that angle.

THOMAS W. ROLPH. 

